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MBL2 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

MBL2 gene

The MBL2 gene provides instructions for a protein that helps the immune system recognize and destroy foreign invaders like bacteria and viruses.

Normal Function

The MBL2 gene provides instructions for making a protein that assembles into a protein complex called mannose-binding lectin. Functional mannose-binding lectins are made up of two to six protein groups called trimers, which are each composed of three of the protein pieces (subunits) produced from the MBL2 gene. This protein complex plays an important role in the immune system's response to foreign invaders (pathogens).

Mannose-binding lectin recognizes and attaches (binds) to sugars, such as mannose, fucose, and glucose, that are found on the surface of bacteria, viruses, and yeast. This binding turns on (activates) the complement system, which is a group of immune system proteins that work together to destroy pathogens, trigger inflammation, and remove debris from cells and tissues. Attachment of mannose-binding lectin also targets the pathogen to be engulfed and broken down by special immune cells. Recognition of foreign invaders by mannose-binding lectin provides one of the body's first lines of defense against infection.

Health Conditions Related to Genetic Changes

Mannose-binding lectin deficiency

Several common mutations of the MBL2 gene can lead to a condition called mannose-binding lectin deficiency. People with this condition have low levels of mannose-binding lectin and may be susceptible to recurrent infections. Several of the disease-associated mutations occur in a region of the MBL2 gene known as exon 1 and result in a change to single protein building blocks (amino acids) in the mannose-binding lectin subunit. Other mutations occur in an area of DNA near the MBL2 gene called the promoter region, which helps control the production of the mannose-binding lectin subunit.

The change of a single amino acid in the mannose-binding lectin subunit eliminates its ability to assemble into the functional mannose-binding lectin. Similarly, certain mutations in the promoter region of the MBL2 gene reduce production of the mannose-binding lectin subunit, leading to a decreased number of subunits available for protein assembly and a reduction in the amount of functional protein. With decreased levels of mannose-binding lectin, the body does not recognize and fight foreign invaders efficiently. Consequently, infections can be more common in people with this condition.

Other Names for This Gene

  • COLEC1
  • collectin-1
  • HSMBPC
  • mannan-binding lectin
  • mannose-binding lectin (protein C) 2, soluble
  • mannose-binding lectin (protein C) 2, soluble (opsonic defect)
  • mannose-binding lectin 2, soluble (opsonic defect)
  • mannose-binding protein C
  • mannose-binding protein C precursor
  • MBL
  • MBL2_HUMAN
  • MBL2D
  • MBP
  • MBP-C
  • MBP1

Genomic Location

The MBL2 gene is found on chromosome 10.

Frequently Asked Questions

Mannose-binding lectin is primarily involved in the innate immune response to bacteria, fungi, and some parasites by activating the complement system and promoting phagocytosis. While it plays a role in viral defense, the impact of MBL deficiency on viral infections is generally less pronounced than on bacterial infections. Individuals with MBL deficiency are more commonly affected by recurrent bacterial infections, such as otitis media (ear infections) and sinusitis, rather than frequent or severe viral illnesses.
Not necessarily. Many individuals with MBL2 mutations and low levels of mannose-binding lectin remain healthy and do not experience significant health issues. However, those with severe deficiency are at a higher risk for recurrent bacterial infections, particularly in the respiratory tract, sinuses, and ears. The risk is highest in early childhood, and some people may also be more susceptible to certain fungal or parasitic infections. Regular monitoring and prompt treatment of infections are recommended for those with confirmed deficiency.
Yes, genetic testing can identify specific mutations in the MBL2 gene, such as those in exon 1 or the promoter region, that lead to reduced production of mannose-binding lectin. Additionally, a standard blood test can measure the actual concentration of MBL protein in the serum. Clinicians often use both methods: genetic testing to confirm the specific variant and protein level testing to assess the functional impact. A low protein level combined with a known pathogenic mutation provides a definitive diagnosis of MBL deficiency.
Yes, it is crucial to inform your healthcare provider if you have a known MBL2 mutation or MBL deficiency. This information is vital because procedures like surgery or treatments that suppress the immune system (such as chemotherapy or certain autoimmune medications) can increase the risk of serious infections. Your medical team may take extra precautions, such as prescribing prophylactic antibiotics or monitoring more closely for signs of infection, to mitigate these risks.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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